In principle, it is already known to supply an LED path, which may have one or more LEDs connected in series, with electrical power from an operating device having a constant current source. It is likewise known that, in order to generate this electrical power, the operating device comprises a resonant converter, for example in the form of an LLC circuit.
The invention now relates to a circuit in which an LLC circuit is supplied from a PFC circuit. The output voltage of the LLC circuit is subjected to potential isolation via a transformer, for example, and is then supplied, for example, to a further converter stage, in particular a constant current or buck converter, which in turn supplies the LED path.
In this case, the aim of the LLC circuit is to generate a constant voltage on the secondary side of the potential isolation. In this refinement, it is known that this constant voltage can be generated in such a manner that the LLC circuit is operated at a constant frequency in the range of resonance.
The object of the present invention is now to improve the electromagnetic compatibility (EMC) of such an operating device having a resonant converter.